title: Promoter methylation and expression of TIMP3 gene in gastric cancer.
abstract: BACKGROUND
  Gastric carcinoma development is a multi-stage process that involves more than one gene. Aberrant changes in DNA methylation are considered as the third mechanism that leads to anti-oncogene inactivation, which plays an essential role in tumor development. In this study, we assessed the relationship among the aberrant methylation of the promoter CpG islands of tissue inhibitor of metalloproteinase 3 (TIMP3) gene, its protein expression, and the clinicopathological features of gastric adenocarcinoma.
  
  
  METHODS
  The methylation status of the promoter CpG islands and the protein expression of TIMP3 gene in tumors and adjacent normal mucosal tissues of 78 patients with gastric adenocarcinoma were detected by methylation-specific PCR (MSP) and immunohistochemistry.
  
  
  RESULTS
  The CpG island methylation of TIMP3 was detected in tumor tissues, cancer-adjacent tissues, and lymph nodes with metastasis. In increasing order, the hypermethylation frequency of these tissues were 35.9% (28 of 78 non-neoplastic tissues), 85% (17 of 20 early-stage cases), 89.7% (52 of 58 progressive-stage cases), and 100% (78 of 78 metastatic lymph node). A marked difference was found between tumors and non-neoplastic tissues (P<0.05), but no difference existed among the subgroups of tumors (P>0.05). Immunohistochemistry analysis confirmed TIMP3 down-regulation in tumor tissues. The rate of TIMP3 gene expression was 100% in non-neoplastic tissues but apparently decreased to various extents at different stages, i.e., decreased to 30% (6/20) at the early stage, to 3.4% (2/58) at the progressive stage, and to 0% (0/78) in metastatic lymph nodes. Among the 70 tumor tissues with negative TIMP3 expression, 64 (91.4%) were hypermethylated and 6 were unmethylated (8.6%), indicating a significant association between hypermethylation and reduced or negative TIMP3 expression (P<0.01).
  
  
  CONCLUSIONS
  The hypermethylation of the promoter region in CpG islands is the main mechanism of TIMP3 gene expression and may provide evidence for the molecular diagnosis and stage evaluation of gastric cancer.
  The virtual slides for this article can be found here: http://www.diagnosticpathology.diagnomx.eu/vs/1756134016954958.
authors.affiliation: Department of Cardiovascular and Thoracic Surgery, TianJin Medical University General Hospital, 154 AnShan Road, HePing Section, TianJin 300052, China. guanzy69@163.com
authors.forename: ZhiYu
authors.initials: Z
authors.lastname: Guan
authors.forename: Jun
authors.initials: J
authors.lastname: Zhang
authors.forename: ShiHui
authors.initials: S
authors.lastname: Song
authors.forename: DongQiu
authors.initials: D
authors.lastname: Dai
mesh_terms: D000230:Adenocarcinoma / Q000737:chemistry / Q000235:genetics* / Q000556:secondary; D014408:Biomarkers, Tumor / Q000032:analysis / Q000235:genetics*; D018899:CpG Islands; D019175:DNA Methylation; D005260:Female; D015972:Gene Expression Regulation, Neoplastic; D020022:Genetic Predisposition to Disease; D006801:Humans; D007150:Immunohistochemistry; D008207:Lymphatic Metastasis; D008297:Male; D008875:Middle Aged; D009367:Neoplasm Staging; D010641:Phenotype; D016133:Polymerase Chain Reaction; D011401:Promoter Regions, Genetic; D013274:Stomach Neoplasms / Q000737:chemistry / Q000235:genetics* / Q000473:pathology; D019717:Tissue Inhibitor of Metalloproteinase-3 / Q000032:analysis / Q000235:genetics*
chemical_list: D014408:Biomarkers, Tumor; C088390:TIMP3 protein, human; D019717:Tissue Inhibitor of Metalloproteinase-3